The present invention relates to a device for applying a coating of an adhesive substance to the downward facing external surface of an endless belt in a screen printing machine, at least comprising an elongated trough for holding a stock of an adhesive substance, means for bringing the adhesive substance into contact with said surface, and doctor means extending in the lengthwise direction of the trough, for setting a desired application of adhesive substance to said surface.
Such a device is known and is used for the application of an adhesive substance to an endless belt present in, for example, a screen printing device. The endless belt in such a screen printing device is used for guiding, for example, a textile web, while rotary screen printing stencils roll along the surface of the textile material lying on the belt, forming dye patterns in the process. In order to ensure that the textile material remains in the same position relative to the rotary silk screen stencils during the printing, which is particularly important if several colors have to be printed in succession in register, it is usual to fix the textile web relative to the moving endless belt by means of a temporary adhesive substance. The adhesive substance to be used, for example polyvinyl alcohol, is generally applied in the form of an aqueous solution to the underside of the belt not in contact with the stencils and the textiles to be printed. The textile web material to be stuck to the belt is brought into contact with the surface of the moving belt under light pressure and adheres in that way; at the end of the horizontal path leading below the screen printing stencils, the textile material is pulled away from the adhesive layer again. As the belt turns further, the adhesive layer, which has served its purpose, is generally removed from the belt by washing, after which a new, fresh adhesive layer is applied. In the known devices of the type indicated, the means for bringing the adhesive substance into contact with the surface of the endless belt are generally formed by a roller rotating in the trough, which roller is in contact with the downward facing surface of the endless belt; in that way the adhesive substance is applied to the surface of the belt from a stock in the trough; the doctor means, which are disposed downstream relative to the roller, viewed in the direction of movement of the belt, then set the thickness of the layer of adhesive substance.
Through the presence of the transfer roller(s) for the adhesive substance, such a known device has the disadvantage that it is heavy as a whole and is therefore difficult to handle, while a large space is also necessary for setting up the device.